教学方

康仕仲

原臺灣大學土木工程學系教授 (Professor)

脚本

Hello, everyone, today, we are going to look at the implementation of 2D sketches. We are going to draw two objects today. First, as you can see here on the left, a small shelf unit with drawers. We are going to learn how to draw this shelf. Then, on the right, there is a pair of scissors from my desk. I would like you to learn how to draw this pair of scissors. We will use a very speedy method, a method that is very common among engineers, to present these two objects in sketches. So first, we look at this desktop shelf unit. You can first observe it, its structure is quite simple, you see a rectangle with lines in it, and there are two drawers at the bottom. To draw such an object, there are a few simple rules, first and foremost, it must be drawn in the correct proportion. And how can we make sure it is drawn in correct proportion? Here is a simple technique: draw based on your visual. It is easy to do so with a picture, you can measure it, what's the ratio of length and width. So, first you look at the shelf unit, what is the ratio of its length and width. Then, you use that ratio and draw an outline of the shelf unit. Another important technique is, use the construction lines. So, in the sketch, use construction lines, and form a frame for the object. Then, use the ratios to draw the important characteristics of it. As you can see, this shelf unit, it is divided vertically into two parts, the left is bigger than the right. So, you can do an estimate measure of this ratio. From what I can see, it is about 3:2. You can do a quick measurement of it. When you are drawing it, how do you get 3:2? You can use your pencil. The sharpened end of the pencil has a length which you can use. Maybe use that length times three, and that same length times two, you will draw 3:2. In this way, you can get a proportion which is quite accurate. So you can see that, the drawer at the bottom and this larger space on top, what is the proportion, probably about 1:4 or 1:5, so you can sketch accordingly. So you have a frame and now you can trace the important lines with darker lines. Now, we are able to draw the whole shelf unit. Next, let us see how to draw this pair of scissors. At first look, it may seem quite difficult. Because it has a lot of curves, and there are many details so we don't know where to start. If I ask you to draw this, you may just start from the left hand side and slowly move across the paper to the right hand side, to form the shape of the scissors. I don't know how it will turn out for you, but usually, it's not that good. The proportion is usually not so accurate. In Engineering Graphics, we emphasise on proportion very much. So, for such a pair of scissors, you can first use a construction lines to form a few boxes for the outlines. Then, for example, you can divide the scissors into two parts. The handle use a bigger box to frame it, the blade use a slimmer long box to frame it. With two boxes, we have successfully divided a complicated scissors shape into two major parts. Well, here is another small tip, after you have a well-proportioned outline, don't just focus on the scissors, You can observe the parts to be removed within the boxes, that is, the empty spaces between the construction lines and the scissors. These spaces are in simpler shapes. As we can see here on the top-left corner, between the handle and the box, there is a space which is similar to a triangle, though with a bit of curve. This part need to be removed. Then, there is another triangle here at the handle to be removed. After we removed a few triangles, we can see that the shape of the scissors started to emerge. So you can draw the scissors gradually now. From the parts that are removed, you are going to get a rough shape of the scissor, then, you will draw the shape of the scissors with faint construction lines, After that, use thicker lines to trace, or if you are using a pencil, apply more force to give darker lines and trace the shape. This is not very difficult, should be done in a minute or two. Use construction lines to draw the boxes to frame the scissors, removed the unwanted parts, and draw the outline with faint lines, lastly, trace the outline. There you are, we have finished drawing the scissors. Are you through? This is the scissors on my desk, you can also try to draw the things on your desk. Especially those with weird shapes, such as the tape holder, stapler, etc. Try drawing them. I believe you will be surprised that you have the ability to draw these things in close resemblance. Well, here I have another picture for your practice: my stapler. Try to draw this stapler well. Just in the same way, use a box to frame it, remove the unwanted part, then, and trace the outline. I believe you can do it very well. Lastly, I would like to draw a conclusion. In order to draw something in close resemblance to the object itself, there are a few simple tips. First, you need to have construction lines to assist you, so, use some boxes and frame the object, divide it into a few smaller parts. After you have these boxes, you can go into details. Secondly, you must maintain the correct proportion. And well, this is also related to the construction lines we talked about. First you observe an object, you must use the concept of construction lines and frame it. Then, you draw according to its proportion, the length and width. The boxes are usually squares or parallelograms. We human-being usually have an instinct about lengths. So as long as you get the proportion of the frame, you can draw it pretty well. How do we get the correct proportion? You can use your thumb, your little finger, or the sharpen part of the pencil, or the width of the thumb etc, all simple tools that you can acquire immediately as you draw, you can use them as scale. You can use several things, and you can draw objects according to its proportion. Then, there is a simple principle, the Subtraction Principle. When the object you draw is complicate, you can frame it with boxes and remove the parts you do not want. You will be surprised by how simple these shapes are: triangles, little squares and circles here and there. You frame the object with a bigger box, minus the parts of you don't want, you get a rough shape of the object. Just like the way we have draw the scissors today. So from some basic geometrical shapes, and polish them, you can draw something that resembles the real thing. So these are some principles of 2D sketches. There are some more useful methods, I hope you will practice a lot and you will get better and better in sketching.